Conventionally, in the medical field, when injecting drug solution or the like into the patient, or proceeding fluid transfusion, blood transfusion, artificial dialysis, blood collection or the like for the patient, a needle assembly equipped with a hollow or solid needle for puncturing has been used as a medical instrument for the procedure. Such a needle assembly typically has a structure in which the needle projects from a needle hub. As the needle hub, for example, a needle base attached to a male luer of a syringe, an inner needle hub, a syringe hub integrally formed with a distal end of the syringe are employed so as to provide needle assemblies with various types of structures for use in various procedures.
Meanwhile, after using the needle assembly, if the removed needle tip is left exposed, there is a risk that inadvertent pricking accidents may occur where physicians, nurses, or disposal contractors might mistakenly prick their fingers or the like with the exposed needle tip. Once such an inadvertent pricking accident occurs, there is a risk of infectious diseases transmitted by the blood adhered to the needle tip, or inadvertent ingestion of the drug solution adhered to the needle tip.
Thus, a needle assembly provided with a needle tip cover for covering the needle tip after use has been suggested. For example, Japanese Domestic Publication of International Patent Application No. JP-A-2005-501665 (Patent Document 1) describes such needle assembly for which, after use of the needle assembly, a cap externally disposed about a needle is configured to be moved to the distal end side of the needle so as to cover the needle tip. Also, when the needle tip is covered by the cap, the needle tip is configured to be deviated from the needle through-hole to the direction of eccentricity to be covered so that the needle tip is not seen through the needle through-hole of the cap.
However, with the needle assembly of conventional construction described in Patent Document 1, in order to cover the needle tip by deviating it from the needle through-hole, the cap is connected with the syringe main body by an elastically deformable member, so that the cap is urged in the direction of eccentricity with respect to the injection needle all the time. Therefore, while the cap is moved to the distal end side of the needle after use of the needle assembly, the inner surface of the through hole of the cap pressed against the side surface of the injection needle almost scrapes the outer surface of the injection needle.
Consequently, the blood, drug solution or the like adhered to the outer surface or the distal end of the injection needle is scraped off while the cap is moved to the distal end side of the needle, and is likely to be left adhered on the surface of the cap covering the needle tip. Accordingly, there is a risk that the blood, drug solution or the like adhered to the surface of the cap may be further transmitted to other medical instruments or the fingers or the like of the nurses, or scatter around.